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Commit 7bdb0d18 authored by Tristan Ye's avatar Tristan Ye Committed by Joel Becker
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ocfs2: Add a mount option "coherency=*" to handle cluster coherency for O_DIRECT writes. 



Currently, the default behavior of O_DIRECT writes was allowing
concurrent writing among nodes to the same file, with no cluster
coherency guaranteed (no EX lock held).  This can leave stale data in
the cache for buffered reads on other nodes.

The new mount option introduce a chance to choose two different
behaviors for O_DIRECT writes:

    * coherency=full, as the default value, will disallow
                      concurrent O_DIRECT writes by taking
                      EX locks.

    * coherency=buffered, allow concurrent O_DIRECT writes
                          without EX lock among nodes, which
                          gains high performance at risk of
                          getting stale data on other nodes.

Signed-off-by: default avatarTristan Ye <tristan.ye@oracle.com>
Signed-off-by: default avatarJoel Becker <joel.becker@oracle.com>
parent 75d9bbc7

Documentation/filesystems/ocfs2.txt

+7 −0
Original line number Diff line number Diff line
@@ -87,3 +87,10 @@ dir_resv_level= (*) By default, directory reservations will scale with file 
			reservations - users should rarely need to change this

			value. If allocation reservations are turned off, this

			option will have no effect.

coherency=full  (*)	Disallow concurrent O_DIRECT writes, cluster inode

			lock will be taken to force other nodes drop cache,

			therefore full cluster coherency is guaranteed even

			for O_DIRECT writes.

coherency=buffered	Allow concurrent O_DIRECT writes without EX lock among

			nodes, which gains high performance at risk of getting

			stale data on other nodes.

fs/ocfs2/file.c

+27 −2
Original line number Diff line number Diff line
@@ -2225,6 +2225,8 @@ static ssize_t ocfs2_file_aio_write(struct kiocb *iocb, 
	struct file *file = iocb->ki_filp;

	struct inode *inode = file->f_path.dentry->d_inode;

	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

	int full_coherency = !(osb->s_mount_opt &

			       OCFS2_MOUNT_COHERENCY_BUFFERED);



	mlog_entry("(0x%p, %u, '%.*s')\n", file,

		   (unsigned int)nr_segs,
@@ -2248,14 +2250,37 @@ static ssize_t ocfs2_file_aio_write(struct kiocb *iocb, 
		have_alloc_sem = 1;

	}



	/* concurrent O_DIRECT writes are allowed */

	rw_level = !direct_io;

	/*

	 * Concurrent O_DIRECT writes are allowed with

	 * mount_option "coherency=buffered".

	 */

	rw_level = (!direct_io || full_coherency);



	ret = ocfs2_rw_lock(inode, rw_level);

	if (ret < 0) {

		mlog_errno(ret);

		goto out_sems;

	}



	/*

	 * O_DIRECT writes with "coherency=full" need to take EX cluster

	 * inode_lock to guarantee coherency.

	 */

	if (direct_io && full_coherency) {

		/*

		 * We need to take and drop the inode lock to force

		 * other nodes to drop their caches.  Buffered I/O

		 * already does this in write_begin().

		 */

		ret = ocfs2_inode_lock(inode, NULL, 1);

		if (ret < 0) {

			mlog_errno(ret);

			goto out_sems;

		}



		ocfs2_inode_unlock(inode, 1);

	}



	can_do_direct = direct_io;

	ret = ocfs2_prepare_inode_for_write(file, ppos,

					    iocb->ki_left, appending,

fs/ocfs2/ocfs2.h

+3 −0
Original line number Diff line number Diff line
@@ -263,6 +263,9 @@ enum ocfs2_mount_options 
						   control lists */

	OCFS2_MOUNT_USRQUOTA = 1 << 10, /* We support user quotas */

	OCFS2_MOUNT_GRPQUOTA = 1 << 11, /* We support group quotas */



	OCFS2_MOUNT_COHERENCY_BUFFERED = 1 << 12 /* Allow concurrent O_DIRECT

						    writes */

};



#define OCFS2_OSB_SOFT_RO			0x0001

fs/ocfs2/super.c

+15 −0
Original line number Diff line number Diff line
@@ -177,6 +177,8 @@ enum { 
	Opt_noacl,

	Opt_usrquota,

	Opt_grpquota,

	Opt_coherency_buffered,

	Opt_coherency_full,

	Opt_resv_level,

	Opt_dir_resv_level,

	Opt_err,
@@ -205,6 +207,8 @@ static const match_table_t tokens = { 
	{Opt_noacl, "noacl"},

	{Opt_usrquota, "usrquota"},

	{Opt_grpquota, "grpquota"},

	{Opt_coherency_buffered, "coherency=buffered"},

	{Opt_coherency_full, "coherency=full"},

	{Opt_resv_level, "resv_level=%u"},

	{Opt_dir_resv_level, "dir_resv_level=%u"},

	{Opt_err, NULL}
@@ -1452,6 +1456,12 @@ static int ocfs2_parse_options(struct super_block *sb, 
		case Opt_grpquota:

			mopt->mount_opt |= OCFS2_MOUNT_GRPQUOTA;

			break;

		case Opt_coherency_buffered:

			mopt->mount_opt |= OCFS2_MOUNT_COHERENCY_BUFFERED;

			break;

		case Opt_coherency_full:

			mopt->mount_opt &= ~OCFS2_MOUNT_COHERENCY_BUFFERED;

			break;

		case Opt_acl:

			mopt->mount_opt |= OCFS2_MOUNT_POSIX_ACL;

			mopt->mount_opt &= ~OCFS2_MOUNT_NO_POSIX_ACL;
@@ -1550,6 +1560,11 @@ static int ocfs2_show_options(struct seq_file *s, struct vfsmount *mnt) 
	if (opts & OCFS2_MOUNT_GRPQUOTA)

		seq_printf(s, ",grpquota");



	if (opts & OCFS2_MOUNT_COHERENCY_BUFFERED)

		seq_printf(s, ",coherency=buffered");

	else

		seq_printf(s, ",coherency=full");



	if (opts & OCFS2_MOUNT_NOUSERXATTR)

		seq_printf(s, ",nouser_xattr");

	else